Sometimes basic mail merge has problems with cells that contain a dash (-) such as a plus-4 zipcode (74370-0505) – it refuses to print anything for that area, or switches to gobbledygook. Simple solution for zips – make a base cell for your code and a +4 cell for the additional numbers and when setting up mail merge don’t forget to place a dash between the tags. For small lists and rural areas, some just use the base zip, but that sometimes slows delivery.